Sandbox 43



Trypsin
Trypsin is a serine protease that is used in the body to hydrolyze proteins. It is produced in the pancreas as its inactive zymogen form trypsinogen. It is produced inactively so as to not destroy the organ that produces it. Trypsin is used to cleave peptide bonds in proteins on the carboxyl side of the arginine or lysine. Its optimal operating temperature is 37&deg C and around a pH of 8

Structure and Stability
Trypsin is composed of 229 amino acids. Its secondary structure is composed of two alpha helices (pink) and two beta sheets (yellow). In addition to these patterns, trypsin has very distinct polar (purple) and nonpolar (gray) regions. The nonpolar areas are the hydrophobic molecules that are trying to stay away from water in the solvation sphere. The polar areas are hydrophilic and are on the outside of the molecule and readily interact with the solvation sphere.

Within the molecule, three disulfide bonds exist for stability. These bonds occur between the amino acids cysteine as can be seen here. Other intermolecular forces are at work within the molecule as well, such as Hydrogen bonding. This last link shows hydrogen bonding around the disulfide bonds specifically.

The composition of Trypsin is all protein with a few molecules of inorganic sulfate groups(blue) to keep it in a constant conformation.

Function
Trypsin has a catalytic triad in it, consisting of histidine-57, aspartate-102, and serine-195. Together these residues make the active site nucleophilic. It is used to cleave arginine or lysine on the C- terminal side of the amino acid residues. The exception to this is when either is followed by a proline, due to steric hindrance. The rate is slower if the residue is bound to an acidic residue as well. The active site of trypsin is histidine-46 and serine-183. The zymogen of trypsin, trypsinogen is not activcated until it reaches the small intestine. Once activated, it will proceed to cleave bonds. However, if it has nothing to cleave, it will begin to cleave itself. This phenomena is called autolysis. To prevent this from happening, trypsin should be stored in either a really cold location, well below freezing (which is not biologically possible), or at a pH below 2 (which is biologically possible). By storing it like this, it is deactivated and will not cleave anything.

A severe condition exists when the body does not produce trypsin correctly. This condition is cystic fibrosis. This disease hinders the transport of trypsin from the pancreas to the small intestine, not allowing for the digestion of proteins.

Trypsin is used to break down breast milk and baby food as it is a protein cleaver. This is especially useful for infants, who may not have developed as strong proteases. This allows for easy digestion of food.